Buck regulator switching power supplies typically include a bootstrap capacitor used to boost a voltage at a gate of a high side MOSFET. The purpose of the bootstrap capacitor is to allow the high side MOSFET to be enhanced “on” since its gate voltage must be greater than the voltage normally available in the application.
In certain operating conditions, the bootstrap capacitor of the buck regulator switching power supply can lose its charge. When this happens, the power stage does not function properly, and in some circumstances, the power stage can latch “off”.
There is desired an improved buck regulator switching power supply that ensures the bootstrap capacitor is properly recharged, particularly when the buck regulator switching power supply has a high duty cycle to provide large output voltages, including outputs very close to the input voltage.